Electron discharge device employing hollow resonator



Sept. 10,. 1946. I 4.5 CAIRNS 2,407,607

ELECTRON DISCHARGE DEV-ICE EMPLOYING HOLLOW RESONATOR FiledMarch 13-, 1944 Jo'm EJwin IQ-l to Cai ns RTTORNEY Patented Sept. 10, 1946 UNITED STATES ATENT OFFICE ELECTRON DISCHARGE DEVICE EMPLOYING HOLLOW RESONATOR Application March 13, 19%, Serial No. 526,184 In Great Britain August 8,1941

4 Claims. 1

This invention relates to electron discharge devices of the type employing a hollow resonator. and having a reflecting or target electrode disposed in proximity to the hollow resonator.

It is of course necessary in manufacturing such devices to effect an adequate degassing operation of the metal parts of the device within the envelope thereof and unless recourse may be had to eddy-current heating of the metal parts the degassing is a slow process. Usually the reflecting or target electrode comprises a small flat or partially spherical electrode which is arranged close to the metallic structure of an adjacent hollow resonator. When eddy-current heating of the hollow resonator for degassing purposes is effect- 1 ed, it is of course necessary that thereflecting or target electrode should also become heated for degassing purposes, but it is found that owing to the large metallic area of the hollow resonator very little current is induced in the reflecting or target electrode with the result that this electrode does not become adequately degassed.

The present invention is concerned with improving the construction of the reflecting or target electrode to enable it to be adequately heated for degassing purposes when the resonator is heated by eddy currents.

According to the invention there is provided an electron discharge device employing a hollow resonator disposed partly or wholly within an envelope and having a reflecting or target electrode also within said envelope and in such close proximity to said resonator that owing to the larger mass of said resonator little current can be induced in the reflecting or target electrode when subjected to eddy current heating simultaneously with the resonator and wherein said reflecting or target electrode is provided with one or more metallic extensions projecting away from the resonator for the purpose of providing a substantially larger area than would otherwise be the case so that said reflecting or target electrode proper can be adequately heated for degassing purposes when the resonator and said extension or extensions are simultaneously heated by eddy currents.

In order that the said invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the accompanying drawing in which:

Figure 1 illustrates diagrammatically a portion of an electron dischargedevice employing a hollow resonator and a reflecting or target electrode constructed in accordance with the invention, and

Figure 2 illustrates a similar View of an electron discharge device on an enlarged scale embodying further form of reflecting or target electrode according to the invention.

Referring to Figure 1 of the drawing, the reference numeral 3 indicates the envelope oi the device the end caps or closures of which are omitted. The hollow resonator comprises a pair of discs t and 5 which are sealed to the envelope, the peripheries of the discs being closed by an annular metallic rim, not shown, to complete the formation of the resonator. The discs 4 and 5 at their central portions within the envelope 3 are re-entrant and are provided with oppositelydisposed apertures in known manner. An electron gun 55 illustrated diagrammatically is supported in the envelope by a pair of mica discs I. lhe electron gun is adapted to produce a beam of electrons which is caused to pass through the apertures in the hollow resonator into the vicinity of a reflecting or target electrode 8, which is disposed in proximity to the disc 5 of the resonator. The reflecting or target electrode 3 is of partially spherical form and is supported by a support rod H3 which, in turn, is carried by a pair of mica discs ii. As mentioned above, it is foundwith known forms of reflecting or target'electrodes that, when it is desired to effect heating thereof for degassing purposes by eddy-current heating, very little current is induced in the reflecting or target electrode due to the larger adjacent mass of the resonator. According to the invention, for the purpose of enabling the reflecting or target electrode to be adequately heated by eddy currents simultaneously with the heating of the resonator, the periphery of the electrode 8 is provided with a metallic extension !2 which projects away from the resonator, as shown, so as to provide a substantially larger area than is the case where no such extension is employed. The extension may be a cylindrical extension and may be bifurcated or castellated so that, in effect, 'a plurality of fins are provided projecting away from the resonator. In one example, where the diameter of the reflecting or target electrode is flve-eighths of an inch the cylindrical extension may be approximately three-eighths of an inch long. Wits such a construction the hollow resonator and the reflecting or target electrode may b eddy-current heated from one side of the device simultaneously, and by appropriately dimensioning the cylindrical extension it can be arranged that the reflecting or target electrode and the hollow resonator all reach approximately the same temperature when heated simultaneously with the same heater coil.

Figure 2 of the drawing illustrates an embodiment of the invention in which the reflecting or target electrode is disposed close to the aperture in the disc of the resonator. In this form of the invention the reflecting or target electrode comprises a cup-shaped electrode l3 which is arranged within the re-entrant portion of the disc 5 and is supported in the end of a sleeve I4 which constitutes, in effect, an extension of the reflecting or target electrode l3, the extension extending away from the hollow resonator and afiording a substantially larger area whereby the reflecting or target electrode 13 can be adequately heated for degassing purposes simultaneously with the heating of the discs 4 and 5 of the resonator. The cylindrical extension M is supported by a pair of mica discs [5.

During eddy-current heating of the resonator and the reflecting or target electrode, it will be appreciated that current will be induced in the extensions [2 and M and the reflecting or target electrode proper will then, in general, be heated by conduction from the extensions. It is only required to degas the metallic parts within the envelope so that, in thiscase, the peripheral rim for the resonator will be applied to the discs 4 and 5 after the degassing operation has been completed.

What I claim is:

1. An electron discharge device having an envelope containing a cathode for supplying a stream of electrons, and an oppositely disposed electrode toward which said electrons are directed, and a cavity resonator extending trans versely of the electron path between said cathode and said other electrode and having apertures through which said electrons are directed, said other electrode being spaced closely adjacent 'said resonator and having conducting means ex tending away from said resonator, electrically and conductively connected to said other electrode whereby said other electrode may be heated by eddy currents for degassing said other e1ectrode.

2 An electron discharge device having an envelope containing a cathode for supplying a stream of electrons, and an oppositely disposed 4 electrode toward which said electrons are directed, and a cavity resonator extendingtransversely of the electron path between said cathode and said other electrode and having apertures through which said electrons are directed, said other electrode being spaced closely adjacent said resonator and having conducting means extend ing away from said resonator, electrically and conductively connected to said other electrode whereby said other electrode may be heated by eddy currents for degassing said other electrode, said conducting means comprising an elongated collar-like element.

3. An electron discharge device having an em velope containing a cathode for supplying a stream of electrons, and an oppositely disposed electrode toward which said electrons are directed, and a cavity resonator extending trans versely of the electron path between said cathode and said other electrode and having'apertures through which said electrons are directed,- said other electrode being spaced closely adjacent said resonator and having conducting means extending away from said resonator, electrically and conductively connected to said other electrode whereby said other electrode may be heated by eddy currents for degassing said other electrode,

said conducting means comprising an elongated collar-like element slotted to provide a plurality of fin-like elements extending parallel to the path of the electron stream and away from said resonator.

4. An electron discharge device having an envelope having a cathode for supplying a stream of electrons and an electrode toward which said electrons are directed, and a cavity resonator ex tending transversely of said envelope and having reentrant portions provided with apertures through which the electron path extends, said electrode being received within one of said reentrant portions but spaced from the wall of said resonator and having an elongated hollow tubular conducting member extending away from and outside of the walls of said resonator Whereby said other electrode may be conductively heated when eddy currents are induced in said elongated conducting portion.

JOHN EDWIN INGLISTON CAIRNS. 

